abstract
Green syntheses employing aqueous solutions of lanthanide chloride, NaOH, and pentafluorobenzoic acid were successfully developed and produced pure dinuclear alpha-Ln compounds, [Ln(L)(3)(H2O)(4)](2)center dot 2H(2)O (L: pentafluorobenzoate) and new ones: eta-Ln, Na[Ln(L)(3)(H2O)(4)]center dot 2H(2)O, and theta-Ln, with Ln: Eu(III), Gd(III), and Tb(III). The synthesis becomes even greener when mechanochemistry is employed because it is quantitative, solventfree, fast (30 min), and energy efficient. The theta-Ln compounds still have unknown composition and structure, so its description and properties are not explored. The eta-Ln compounds are 1-D coordination polymer with only one bridging L, which leads to a large Ln center dot center dot center dot Ln distance (6.865 angstrom). Heteronuclear alpha-Ln(0.50)Ln(0.50) and eta-Ln(x)Ln(1-x) compounds, with x = 0.05, 0.25, 0.50, and 0.75, Ln, Ln ': Eu, Tb, and Gd, have been synthesized by mixing the proper proportion of the lanthanide chlorides in the initial solution. The eta-EuxTb1-x materials present Tb(III) -> Eu(III) energy transfer, which confers interesting luminescent and photophysical properties with relevant potential applications. The color of the emission under UV irradiation can be tuned by the composition of the eta-EuxTb1-x materials as well as by the excitation wavelength. In addition, it was observed a significant increase (ca. 35-260 %) of the D-5(0) Eu(III) emission lifetime in the eta-EuxTb1-x compounds by varying the excitation wavelength.
keywords
ENERGY-TRANSFER RATES; METAL-ORGANIC FRAMEWORKS; EARTH BENZOATE COMPLEXES; CRYSTAL-STRUCTURE; STRUCTURAL VARIATIONS; AQUO IONS; PART I; FLUOROBENZOATES; FLUORINATION; CARBOXYLATES
subject category
Materials Science; Optics
authors
de Souza, VP; Brandao, P; Malvestiti, I; Longo, RL
our authors
Projects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
The authors acknowledge the financial support from the Brazilian agencies Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE) , Conselho Nacional de Desenvolvimento Cientffico e Tecnologico (CNPq) , Financiadora de Estudos e Projetos (FINEP) , Coordenacao de Aperfeicoamento de Pessoal do Nfvel Superior (CAPES) . P.B. gratefully acknowledges the financial support of this work by the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC) . V.P.S. thanks FACEPE for the scholarship (IBPG-0068-3.03/17) . R.L.L. thanks CNPq for the PQ-fellowship (Proc. No. 308000/2022-6) . The authors acknowledge the Laboratorio de Raios-X (DF-UFPE) for the XRD measurements, the Central Analftica (dQF-UFPE) , Central Multiusuario de Espectroscopia do Nordeste (CEMENE) for the spectroscopic measurements, Prof. Ana Paula Paim and Yhasmyn Nunes for ICP OES measurements, Prof. Kelly C. G. da Silva from Laboratorio de Sfntese e Caracterizacao de Filmes Finos (LabFilm) -UFPB for the thermal analyses, and Cemupec-Centro multiusuario de pesquisa e caracterizacao de materiais da UACSA-UFRPE for EDS X-ray microanalysis.